(define (split-high lst)
  (reverse(list-tail (reverse lst) (inexact->exact (floor (/ (length lst) 2))))))

(define (split-low lst)
  (list-tail lst (inexact->exact (ceiling (/ (length lst) 2)))))

(define (merge listA listB)
  (cond ((and (null? listA) (null? listB)) '())
	((null? listA) listB)
	((null? listB) listA)
	((<= (car listA) (car listB)) (cons (car listA) (merge (cdr listA) listB)))
	(else (cons (car listB) (merge (cdr listB) listA)))))

(define (merge-sort lst)
  (cond ((null? lst) '())
	((= (length lst) 1) lst)
	(else (merge (merge-sort (split-high lst)) (merge-sort (split-low lst))))))

(merge-sort `(3 2 1))